There has been heightened interest in developing light activated tissue solders and sealants as a substitute for conventional closure methods such as the fixation of grafts/implants and anastomoses. Advantages include speed of closure, reduced infection due to the elimination of foreign matter, evidence of accelerated wound healing and the ease of use in complex surgery, especially when watertight seals, limited access or small repair size are important factors. Laser activation provides a directed energy source for precise placement of the sealing material and can amplify the crosslinking mechanism for bonding together incisional edges or wound tissue flaps.
Numerous studies have reported the efficacy of light activated materials to join soft tissues. The availability of a variety of laser output powers, wavelengths, which match the optical properties of tissue, as well as the development of protein composites, layered materials and those modified with growth factors, chromophores, or photochemicals have advanced the technology. Applications range from urologic anastomoses, small diameter vascular anastomoses, nerve anastomosis and skin closures.
Photothermal processes modulate the strength of the repair and may reach a precise temperature set by the choice of laser and material composition to obtain protein reconstruction at the glue/tissue interface with minimal damage to peripheral tissue. Some of these glue constructs tend to undergo blood dilution during surgery with mechanical alteration thereby weakening the repair. The stronger adhesives are often brittle, inflexible and not easily adapted to different tissue geometries.
In comparison, photochemical processes involve the breaking of photosensitizer bonds, in the presence of energetic light such as UVA, with the resultant generation of reactive species that catalyze and accelerate the formation of linkages to underlying tissue.
Methods to date have not gained clinical acceptance. The major reasons include the high level of surgeon skill that is required, the strength, toxicity and resorbability of the tissue adhesive, the potential for irreparable laser damage and cost of the laser system.